DE3015970A1 - METHOD AND DEVICE FOR CHANGING THE FORM OF WORKPIECES FROM METAL OR ALLOYS - Google Patents

Description

Method and apparatus for changing the shape

of metal or alloy workpieces The present invention relates to new, improved processes for forming heat-resistant and other metals and alloys.

A currently important field of application for the invention is in the reshaping of turbine and compression blades to either their original or their new designs; and the principles of the invention are accordingly mainly developed with reference to this scope. Included however, it must be understood that this is mainly for the sake of clarity and clarity happens and is not intended to be those in the attached Claims defined to limit the scope of the invention as it should be understood by those skilled in the art become clear from the corresponding areas becomes that the innovative processes are equally good for forming other metallic parts or Components can be used.

It is known that the blades of turbine engines can be damaged by foreign objects, Stress voltages and high temperatures can be damaged or warped. Until a few years ago, these blades were rejected because of blade deformation reduces the efficiency of the engine or causes an irregular gear.

However, because of the high replacement costs for blades, one is looking now according to procedures for blade repairs. For example, in U.S. Patent 3,574,924 a Blade repair process described, which uses the diffusion bonding technique in closed Die operated at relatively high temperatures for relatively long periods of time. However, this method is not used because it is used by the engine manufacturer has not been accepted or approved.

Since the development of the process disclosed in the above-mentioned US patent the inventor has already repaired damaged blades by means of a process, where distorted or damaged blade parts were cut out with suitable ones new parts were replaced, the new parts were welded and the shovel by grinding or machining the original profile have been adjusted.

During this activity the inventor observed that many shovels only warped and no metal was missing and he set himself the task of repairing it such shovels the previously used complex and time-consuming work steps of cutting, welding and grinding and new possibilities to find that can be used to either shovel its original To reproduce shape or to reshape its shape.

In a few words, the invention encompasses the solution to the problem posed a new method and a new device for forming turbine and compressor blades, and pressing the blades against a heated die face, which either reproduces the original blade profile or a new one that is desired Form offers.

Cutting, welding and grinding and the cost and time of execution consequently, all of these measures are omitted.

The solution to this problem created by the invention is of Significance, since the aerodynamics of the engines is a highly theoretical subject, in which consequently a large part of the development work is empirical takes place. Due to the standard forging techniques used to manufacture sample blades Forging to optimize the blade design is time-consuming and costly. In contrast, the invention provides a relatively inexpensive method of modifying aerodynamic ones Profile shapes so that the engine designers can easily find the optimal blade designs for the realization of such advanced operating features as e.g. reduced Engine noise, reduced specific fuel consumption and increased engine thrust can determine (due to rising fuel costs and stricter noise abatement laws will reduce fuel consumption and reduce engine noise levels today ascribed greater importance by the engine manufacturers).

It will be clear to the reader from the foregoing that an essential The main purpose of the present invention is to provide novel, improved ones Methods and devices for restoring the original warped profiles Turbine and compressor blades.

Another equally important purpose of the invention is that Provision of a method and device for reshaping turbine and compressor blades by changing the twists, profiles or tangential displacements of the same.

The principles of the present invention can also be used to advantage for reshaping objects other than turbine and compressor blades into theirs original or new profiles can be applied.

There are other important but more specific purposes of the invention in the provision of methods and devices according to the preceding Purposes with a specific provision or supplement: that they are used for the forming of heat-resistant Metals and alloys can be used; that this makes them relatively economical are that they follow the conventional sequence of cutting and replacing Parting, welding and grinding to reshape the profile of an existing one Eliminate metal part.

Other important objects, features and advantages of the invention are from the accompanying claims and the following detailed description of exemplary embodiments in connection with the accompanying drawing evident, in which: FIG. 1 shows a side view of a muffle for reshaping metallic workpieces in original or new forms according to the principles of the present Invention represents; Figure 2 is a front view of the muffle; Fig. 3 a represents vertical section through the muffle; and FIG. 4 is a perspective Reproduction of a workpiece before and after machining shows that the Ability of the novel process disclosed herein demonstrates the design shape of changing turbine blades; the original blade is on the left and the reshaped one Shovel shown on the right.

Applied to the repair of turbine and compressor blades there is a preparation for the first step in the novel procedure in a review, to determine whether and to what extent a reshaping is necessary.

Blades with twisting or excessive bending or local deformations of not more than 15% can be reshaped by the method according to the invention will.

Blades with local deformations of more than 15% can through Use of hot plate dies within the tolerance limits of the inventive Procedure. This is a well-known method, and it is beneficial applicable together with the invention.

Blades formed or formed by the method disclosed herein to be re-profiled are cleaned using normal methods; for example through an alkali or acid bath and rinsing. After that they are covered with a protective cover overdrawn. In the case of titanium, a commercially available mixture of graphite and molybdenum disulphide is used. This will reduce oxidation if the re-profiling occurs in an air atmosphere takes place. Stand for aluminum, superalloys and other metallic substances other known standard protective covers are available.

The cleaned and coated blades are then put into a post the principles of the invention executed and for example in Figures 1 to 3 Muffle shown and identified by reference numeral 10 entered.

The muffle 10 has a housing or a casing 12 and is carried on a stand 14 made movable by rollers 16.

The muffle 10 has a housing or a casing 12 and is carried on a stand 14 made movable by rollers 16. A cover or a cover 18 is rotatably attached to the housing 12 by hinges 20.

The lid 18 can be opened and closed by a handle 22, the handling of the lid is facilitated by the counterweight 24.

The cover 18 is in the illustrated, closed position an eyebolt 26 and a nut 28 screwed onto the screw can be closed. The screw is rotatably attached to a housing-supported angle piece 30 and extends upward through slots 32 and 34 in the housing and cover, respectively. Attract the nut 28 biases the cover 18 against a rim 36 around the upper open end of the housing.

The muffle housing 12 is made with the shown firebricks or Bricks 40 isolated. A die 42 formed on one side is accommodated in the housing, which has a die face 44, the profile of which is the part to be formed for to give this part the desired shape. The die can either be made of a metal or made of ceramic. Ceramic is preferable because of its size is adjustable and suitable ceramic materials do not change their shape when heated change and have a longer lifespan. A suitable ceramic material is Thermasil 120, a commercially available, castable glass block ceramic.

In the example of application of the invention cited above - the deformation or re-profiling of turbine blades, the glass block becomes the desired blade profile Cast with cutouts of the shrouds and the blade root near the surface the die face are side holes for receiving (by reference numerals 146 in Figure 3) built-in heating elements.

These are used to increase the temperature of the workpiece to be formed used.

Turbine blades typically have both concave and convex Pages. Either a concave or a convex shape can therefore be used for forming Use a die to give the shovel the desired profile. Is preferred a concave die, as this makes it easier for the blade to be in the correct position Can hold. In the case of a concave die, the blade is also used so aligned; that the forming pressure at right angles or so at right angles acts on the concave side of the blade as much as possible. This also helps keeping the shovel in its correct position by limiting its movement.

The part to be formed is created by the electrical heating elements mentioned above 46 (only one of which is shown) is heated by conduction through the die. The typically designed as resistance heating elements and made, for example, of nickel chrome The heating elements produced are embedded in the die in the vicinity of the die face 44. The heating elements are aligned with the cutouts 50 in the muffle housing 12 Terminal blocks 148 supplied with power.

The temperature in the muffle is determined by thermocouples (not shown) monitored, the lines of which extend through openings 52 to the outside of the housing.

As will be seen later, the workpiece to be formed can be under pressure be set by applying fluid pressure medium to an elastic organ and the resulting pressure across the mass of a compliant, force-transmitting Material transmitted to the workpiece.

The pressure medium is through a line equipped with a valve 56 54 is supplied and the pressure is monitored by the manometer 58. The pressure medium can be drained through line 60.

In many areas of application of the invention, the object to be molded also (or instead) by generating negative pressure in the muffle 10 below Pressure to be set. The inside of the muffle can be opened by a safety pin 64 equipped vacuum line 62 are evacuated. The negative pressure in the housing can be monitored by a vacuum gauge 66.

For forming or shaping, a turbine or

Compressor blade (identified by reference number 68 in Figure 3) so placed on the die face 44 of the die 112 that its edges with the engraved positioning lines on the surface. After that, the Support of the lower edge of the foot section, to prevent movement and to Supporting the shroud (or shrouds) of the blade (not shown) Metal pads in the cavities of the die provided to accommodate the latter appropriate.

It is important that the 'blade shrouds receiving cutouts Have enough clearance in the die face so that the shovel is during of the unforming path can move along its longitudinal axis. It is also important that the cutout for the blade root is designed in such a way that the blade root can be kept accurate.

After the shovel has been placed and leveled by pads is, it is covered with a plate 70 of a heat-resistant or refractory material such as refrasil, asbestos, etc. The cavity 72 in the housing 12 above the plate 70 is then coated with a compliant, heat-resistant, pressure-transmitting medium 74 like pieces of refrasil or vermiculite (a thermally expanded partially weathered Mica). Asbestos strips or heat-resistant glass beads can also be used be used.

The compliant material is kept out of contact with the plate 70 Excluded from the part to be formed, an important practical feature of the invention. To be precise, the workpiece is deformed during the forming process using the method described here new methods can be deformed, as illustrated below. As a result, you can Particles of the resilient material (or foreign matter that comes into contact with the workpiece Contact) embed in it or imprint itself on the workpiece. The defect is in both cases due to the harsh conditions under which these components have to work with high efficiency is unacceptable.

After filling the cavity 72, a layer 76 of heat-resistant Rubber or silicone placed over the resilient material. When the muffle lid is closed will and clamped in place by tightening nut 28 is, the layer 76 provides a vacuum or pressure-tight seal and also serves as a pressure transmitting member in the manner described below.

After sealing the muffle, the rubber sealing layer is attached to the top 76 an air pressure of 13.8 to 20.7 kPa and the heating elements 116 is applied power is supplied to heat the workpiece. The temperature is through the above mentioned thermocouples, which are located along the blade when it is in the muffle 10 has been introduced, measured and regulated. When the shovel the When the deformation temperature is reached, the maximum Air pressure applied. Up to 830 kPa overpressure were used.

That transmitted to the part to be molded through the compliant material 74 Heat or pressure cause the metal under a load that is below its elastic limit lies, flows plastically. This plastic flow (resp. Creep forming) allows each blade to conform to the shape of the die face 44 adapts and maintains this.

During the creep forming of metal parts with this process Different combinations of negative and positive pressure with heat can be applied. For example can with a high vacuum (up to 1,105 Pa = 1 bar) in the blade chamber 72 and at standard air pressure on the top of the sealing layer 76 titanium blades Creep deformation to its original shape or a new shape without additional Pressure can be transformed.

Various heating arrangements can also be used.

The blades are used for forming or profiling titanium blades to between 593 0C and 7050C at an overpressure of between 100 and 350 kPa overpressure warmed up. The heating time required is between 30 minutes and 4 hours. When reshaping titanium, it can also be advantageous to heat the part to 315 ° C heat and leave it approx.

Hold at this temperature for 30 minutes before lowering the temperature is increased to the deformation level of 5930C.

During the heating process, it may also be possible in the one with the flexible material 74 filled cavity 72 an inert atmosphere can be maintained. For For this purpose, negative pressures of 0.8 to 1.0 bar and argon gas come into consideration. Both are quite effective in reducing the occurrence of, for example, alpha layer or oxidation of titanium.

After reshaping, the blades are cleaned and then put to use a hatchet to check the twist, the profile and the tangential dislocation examined.

Application of the invention to the forming of titanium jet engine blades is illustrated with the following examples.

EXAMPLE 1 SHOVEL OF A PRATT & WHITNEY JT-9 TURBINE SHOVEL Place on the die face, cover and muffle with vermiculite as described above fill up.

Cover with silicone sealant and close the mold cover.

Increase temperature to 4200C.

Air pressure on top of seal between 314.5 to 70 kPa overpressure raise. Hold temperature and pressure at these levels for 15 minutes.

Increase temperature to 630 ° C and pressure to 240 to 2145 kPa. One Hold at these values for an hour.

Cool to 370 C, open the muffle and remove the shovels.

The blade is shown with its original profile on the left in FIG shown. The blade is shown on the right in this figure after reshaping. A Comparison of the representation before and after processing shows the major changes in shape, in a single work step by using the new forming process can be carried out in metals that are difficult to form.

EXAMPLE II TURBO FAN BLADE FOR GENERAL ELECTRIC CF-6 ENGINE Place the shovel on the face of the die, cover and fill the muffle as described above and seal.

Temperature to 310 ° C and pressure to between 314.5 and 70 kPa overpressure raise. Hold at these levels for 15 minutes.

Increase temperature to between 480 ° C and 530 ° C and for 15 minutes hold on to this value.

Reduce the negative pressure in the muffle to between 0.8 and 1.0 bar.

Increase temperature to 630 C and pressure to 240 to 2145 kPa. Two Hold at this temperature and pressure for hours.

Cool to 370 ° C, release negative pressure, open muffle and shovel remove.

Have the procedures described in the previous examples proved to be effective and rational for the forming of Ti6Al4V blades. It is not critical, however, that these particular methods be followed slavishly; in order to achieve the desired result indicated above, both temperatures and pressures as well as heating times can be changed. Depending on factors how which metal or which alloy is formed can generally be determined by temperatures between 120 ° C and 1090 ° C can be used. Pressures from 10C to 840 kPa and times at forming temperature of 5 minutes to 6 hours are used come. It will be clear to the reader that in the present process there is a relationship exists between temperature, pressure and duration on temperature. Every parameter is selected according to the principles of good metallurgical practice to avoid material damage to be excluded in the forming process.

The application of the process is not limited by the size of the workpieces limited. For example, it can be used to reshape blades in the size range of a length of 2.5 to over 100 cm and a width of 1.25 to over 50 cm are used will.

In the interests of brevity and clarity, the novel procedure is used above mainly with reference to its application to the working of titanium described. However, it is by no means limited to this. Other metallic materials, which can be advantageously reshaped by applying its principles Aluminum, iron, nickel and cobalt and their alloys, superalloys, etc.

For the same reasons, the discussion above dealt with the mostly restoring the original shapes of parts. It leaves however, it can also be used to change the design shape of a part to a new shape apply as indicated above.

For example, to change the twisting of the profile or the tangential offset a shovel to a new design shape, as in the case of the in Figure 4 illustrated shovel happened. In addition, a shovel can be rebuilt to its original one Midline to be reshaped; or the center line can for example be in proportion be moved to the shovel base.

The procedures are similar to those described above, but this will One-sided die profiled on the new blade construction. Quite radical changes in shape can be carried out with a single die will, and by successive application of convex and concave dies even more radical changes are made.

The invention can without departing from the inventive concept or the essential features of the same are carried out in other specific forms. The present embodiments are therefore intended to be exemplary in all respects and not to be considered limiting, the scope of the invention being understood by the appended claims as indicated by the foregoing description will; and it is therefore intended that all changes that come within the scope of the The meaning and scope of equivalency of the patent claims fall, are encompassed thereby.

L e r s e i t e

Claims (18)

P a t e n t a n s p r ü c h e 1) Method of changing the shape of a metallic workpiece, characterized by the following steps: a) the workpiece is placed on a mold surface that has a shape desired in the workpiece; b) the said workpiece is heated at the same time and over a mass of a flexible, heat-resistant pressure-transmitting material on the opposite side of the workpiece Side of the mold surface is pressurized; c) the temperature at which the workpiece is heated, and the pressure applied to it are so in relation to each other matched that thereby the metal of the workpiece plastically at a below its elastic limit lying load in contact with the forehead surface of said die flows and thereby the workpiece the desired shape accepts. 2) Method according to claim 1, characterized in that for generating the treatment pressure for the workpiece the mass of flexible, heat-resistant, pressure-transmitting material sealing on its side opposite the workpiece covered with a flexible element and an overpressure by means of pressure medium this flexible, covering element is exercised. 3) Method according to claim 1 or 2, characterized in that the Mass of resilient, heat-resistant, pressure-transmitting material on their Workpiece opposite side covered sealingly with a flexible element and that during or during the application of the treatment pressure in the sealed, the workpiece and the mass of flexible, heat-resistant, pressure-transmitting Material receiving space will generate a negative pressure. 4) The method according to claim 3, characterized in that the the Sealing mass made of flexible, heat-resistant, pressure-transmitting material covering, flexible element is exposed to atmospheric pressure and that in the a vacuum of up to 1.0 bar is generated in the sealed space. 5) The method according to claim 3, characterized in that the Pressure-transmitting material sealingly covering, flexible element by means of pressure medium exposed to an overpressure and at the same time in which the workpiece and the pressure transmitting Mass containing space a negative pressure is generated. 6) Method according to one of claims 1 to 5, characterized in that that the workpiece for a period of time from 5 minutes to 6 hours at a temperature held in the range from 100 to 11000C and under an overpressure of 100 to 840 KPa will. 7) Method according to claim 6 for the treatment of workpieces made of titanium alloy, characterized in that the workpiece is heated to a temperature in the range of 200 is heated to 8000C and the pressure applied to the workpiece is 100 to 300 kPa amounts to. 8) Method according to one of claims 1 to 7, characterized in that that between the workpiece and the mass of resilient, heat-resistant, pressure-transmitting Material a plate made of elastic, heat-resistant material is inserted. 9) Method according to one of claims 1 to 8, characterized in that that a zone in which the workpiece to be treated is located from the surrounding Atmosphere isolated and by maintaining a negative pressure in this zone a neutral environment is created for the workpiece. 10) Method according to one of claims 5 to 8, characterized in that that a zone in which the workpiece to be treated is located from the surrounding Atmosphere and by maintaining an inert gas atmosphere in this Zone creates a neutral environment for the workpiece. 11) Device for changing the shape of a metallic workpiece in the method according to one of claims 1 to 10, characterized by the features: a) a die (42) which has a forming surface with that desired for the workpiece Has shaping forming end face; b) a muffle (12) into which the die t42) is inserted with exposed mold surface (44), with heating device (46) receiving space formed in the area of the die (42) and above the die t42) (72) for the workpiece (68) and a mass (74) made of flexible, heat-resistant, pressure transmitting material; and c) a device for generating a differential pressure via the space receiving the workpiece (68) and the pressure-transmitting mass (74) (72). 12) Apparatus according to claim 11, characterized in that the Heating means includes electrical resistance heating elements (86). 13) Device according to claim 11 or 12, characterized in that that the flexible> pressure-transmitting material made of asbestos, vermiculite or a is made of heat-resistant glass. 14) Apparatus according to claim 11, characterized in that the Die (42) is provided with a concave face part (14Lt), which is the exact Alignment of the workpiece (68) relative to the die (42) is facilitated. 15) Apparatus according to claim 11, characterized in that a Plate (70) made of elastic, heat-resistant material as a cover for the workpiece (68) compared to the mass of flexible, heat-resistant, pressure-transmitting Material (74) is provided. 16) Apparatus according to claim 11, characterized in that the Muffle (12) is equipped with a lid (18) that can be firmly pulled on and a flexible one Sealing and covering element (76) for the mass of pressure-transmitting material (74) is provided. 17) Device according to claim 16, characterized in that in the lid (18) the muffle (12) devices (54, 56, 58, 60) for pressure-controlled insertion and releasing pressure medium are attached. 18) Device according to claim 16 or 17, characterized in that that on the muffle housing devices (62, 64, 66) for pressure-controlled generation of a Negative pressure are provided in the interior of the muffle (12).